Vitamins and Coenzyme 3

Question 1

Coenzyme A

Answer 1

CoA core substituents: 2-mercaptoethyamine is bound to the vitamin panthothenate, which in turn is bound via phosphoester linage to an ADP group, that has an additional 3’-phosphate group. It is derived from a panthothenate, vitamin B

Question 2

CoA group transfer

Answer 2

Acyl group transfer

Question 3

Phosphopanthetheine (prosthetic group of ACP)

Answer 3

esterifies PP’ to to a serine residue of the protein

Question 4

Thiamin pyrophosphate (TPP) structure

Answer 4

core: Pyrimidine ring, +ve thiazolium ring, pyrophosphate group. Business end: Thiazolium group in the C2. TPP is active as a prosthetic group in decarboxylases e.g. Yeast pyruvate decarboxylase, oxidative decarboxylase of alpha keto acids other than pyruvate, and transketolases.

Question 5

Yeast pyruvate reaction mechanism

Answer 5

Ylid - a molecule with oppisite charges on adjacent ions.e.g (+ve)C–N(-ve).

Question 6

pyridoxal phosphate (PLP)

Answer 6

Catalyse reversible reactions (transamination), reaction between amino acid and alpha keto acid.

Question 7

Binding of PLP

Answer 7

PLP is initally covalently bonded to the enzyme, through Schiff-base linkage to a Lys residue at the active site.

Question 8

Biotin

Answer 8

Does not require conversion from a vitamin, its both a vitamin and coenzyme. It is also known as Vitamin B7/H or coenzyme R. Key: 2 penta cycles, with carboxy acid tail. It is a prosthetic group. It attaches to Lys residue by using its carboxy acid tail. Its involved in transfer reactions of carboxyl groups and ATP dependant carboxylase.

Question 9

Tetrahydrofolate

Answer 9

Derived from folate (Vitamin B9). 3 main components: Pterin, PABA, glutamate. Function: transfer of 1 carbon unit. (methyl,methylene,formyl,hydroxymethyl). It can have many isomers, specific to the group it is transfering. Folate is required for DNA synthesis.